In addition to voice communication, data communication via connection to a network such as the Internet has become a main function of a mobile phone.
When performing voice communication, a central processing unit (CPU) provided in a mobile phone converts voice into digital information and transmits the digital information to a base station. Further, central processing unit CPU receives digital information from the base station and executes codec processing for converting the received digital information into voice.
On the other hand, when performing data communication, the CPU executes codec processing for expanding digital information, including compressed information of a still image, a moving image and the like, received from the base station and an access point of WI-FI (registered trademark), and storing the expanded digital information in a non-volatile memory or providing a view of a moving image and the like.
Such mobile equipment as represented by a mobile phone is driven by a battery. Therefore, it is required to have a longer battery run time.
Therefore, during a standby period, a data processing device of a baseband processing unit which performs wireless communication operates intermittently to communicate with a base station and the like. Further, a data processing device of an application processing unit lowers the frequency of a clock supplied to an internal functional block and stops the supply, and lowers the supply of the voltage and stops the supply (refer to PTL 1 and PTL 2).
Further, a flash memory is generally used as a non-volatile memory adopted in such a data processing device. As a measure to lower electric power consumption in this flash memory, electric power consumption at the time of performing writing operation is reduced (refer to PTL 3).